Composite propellants typically comprise (a) a polymeric binder, (b) a bonding agent, (c) a curing agent for the binder, (d) a metallic fuel and (e) an ammonium salt oxidizer. Traditionally, these composite propellants have been prepared by the following procedure:
1. premixing the polymeric binder and bonding agent; PA1 2. admixing the metallic fuel with the premix; PA1 3. admixing a portion of the oxidizer with the mixture produced by step 2; PA1 4. vacuum mixing the mixture produced in step 3; PA1 5. adding a second portion of the oxidizer and vacuum mixing the resulting product; PA1 6. adding a third (and final) portion of the oxidizer and continuing vacuum mixing; PA1 7. optionally, aging the mixture produced in step 6 for about 24 hours; and PA1 8. adding the curing agent and vacuum mixing. PA1 1. mixing a polymeric binder and bonding agent; PA1 2. admixing a portion of the ammonium salt oxidizer with the mixture produced by step 1 and vacuum mixing until substantially all of the ammonia has evolved from the mixture; PA1 3. admixing the remainder of the ammonium salt oxidizer with the mixture produced by step 2; PA1 4. admixing the metallic fuel with the mixture produced in step 3; PA1 5. optionally, aging the mixture produced in step 4 for about 24 hours; and PA1 6. admixing the curing agent with the resulting mixture.
It has now been discovered that if the order of addition of the ingredients in a composite propellant is altered, the viscosity of the propellant during mixing is substantially reduced, removal of ammonia from the propellant is faster and dramatic cost savings (in terms of man-hours and energy required to prepare the propellant) are achieved without sacrificing mechanical or ballistic properties of the finished propellant.